Prevention of corrosive wear of moving metal parts



Patented Aug. 7, 1951 PREVENTION or CORROSIVE warm or MOVING METAL rams Aaron Wachter and Nathan Stillman, Berkeley,

Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application August 12, 1946,- Serial No. 690,068

12 Claims.

The present invention relates to the prevention or inhibition of corrosive wear of moving metal parts, which wear normally occurs during the operation of various types of mechanisms or machinery. More particularly, it relates to inhibiting the corrosive wear of metal parts normally subjected to frictional contact with lubricating media and/or bearing motion upon other metal members of a machine. The moving metal parts or bearing surfaces here referred to are normally corrodible in the presence of water vapor, aqueous condensates, and/or oxidizing agents, e. g. air. More specifically, the present invention pertains to inhibiting such corrosion and wear by the presence, in a liquid and/or vapor phase, of one or more novel vapor phase corrosion inhibitors in the proximity of, or in v actual contact with the moving metal parts. The invention also covers a method of preventing or minimizing such corrosive wear by forming, in

the proximity of the metal parts subjected to friction, an atmosphere containing a corrosioninhibiting agent.

Heretofore, there has been no satisfactory solution to the serious problems of corrosion and concomitanirwear of moving metal parts'in various types of machines. For example, during the normal operation of various moving parts, e. g. in steam engines, steam turbines, pumps, etc., wherein moving metal members are in frictional contact with other metal members, e. g. bearings, guiding channels, cylinders, etc., as well as with lubricating media and/or liquid or gaseous fuels containing water and/or air, corrosion and accompanying wear occurred.

In most instances the presence of water is inevitable or practically unavoidable, and at least a significant part of the wear is thought to be closely related, if not wholly attributable, to the corrosion accruing from the presence thereof. In many cases, steam and air are also present. As a result thereof there is evidence of substan- Most of them, however, possessed one or more defects, for example, insuflicient corrosion-inhibiting action, insuflicient volatility or lack thereof, and the inability to inhibit corrosive wear of metal in contact with either or both liquid and vapor phase media. For these and other reasons, these various attempts were unsatisfactory.

It is therefore an object of the present invention to provide a method which overcomes the above and other deficiencies in the art of preventing corrosive wear of metal parts which are in moving contact with other metal surfaces. An object of the invention is to provide a method which materially improves the efliciency of the normal operation of a machine. Another chief object is to provide prevention of corrosive wear of moving metal parts, particularly those present in various types of machinery. Still another object is to provide a method of inhibiting corrosive A aqueous condensates and/or an oxidizing agent,

more particularly, e. g.,' air oxygen.

It has now been discovered that the above and other objects may be attained by introducing into the proximity of, or into actual contact with the moving metal parts, an organic vapor phase corrosion-inhibitor, preferably one or more salts of I an organic base and of nitrous acid. It has been tial corrosive wear of the moving metal parts and of the surfaces of stationary'metal which contact these moving parts. This detrimental corrosive wear is due at least in part to the presence of air and water vapor and/or condensed water vapor in the engines or machines. Corrosive wear of machine parts, as exemplified'in piston ring wear, results in loss of the requisite close tolerance of the metal parts in the engine this being accompanied by faulty performance, loss of power, and excessive consumption of the lubricating oil. Metal bearings lubricated from a crankcase, by a gravity feed, or by a forced feed system wear out even more quickly.

In the past many attempts have been made to reduce corrosive wear of the various machine parts, for example by the addition of different anti-corrosive materials to the lubricating oils.

' further discovered that the presence of these salts of an organic base and of nitrous acid (organicbase nitrites), and preferably of organic nitrogen-base nitrites, inhibits the corrosive wear of moving metal parts and of the metal surfaces in frictional contact therewith. It has also been discovered that the corrosive wear of metal engine parts, for example, the power-transmitting metal parts and the related metal bearing surfaces of an internal combustion engine, is markedly inhibited by the presence (in the gases, and/or liquid such as the lubricants or fuels normally present in the engine) of an organic vapor phase corrosion inhibitor having a vapor pressure of at least about 0.00002 mm. Hg at 21 C., and preferably above about 0.0001 mm. Hg at 21 C. Additionally it was found that the presence of a volatile organic compound which is capable of yielding a nitrite anion prevents corrosive wear of said metal surfaces. The above organic base nitrites also effectively inhibit corrosive wear of engine arts which corrosion is normally due to the presence of air (oxygen) and water vapor, steam, and/or liquid water during thenormal operation of machinery having metal moving parts. It has been also discovered that the cor- .3 I rosive wear of metal parts which are in moving contact with each other isinhibited by maintain ing in the proximity of said metal Darts an atmosphere containing one or more'vapor phase corrosion-inhibitors, preferably an organic base nitrite. The term "atmosphere," as used herein and in the appended claims, includes matter which may be a fluid, e. g. gas or liquid, or a fluid-like solid, such as a grease.

The employed nitrite salt of an organic base may be the nitrite salt of a primary, secondary, or

tertiary amine, a quaternary ammonium base,

one of the other onium bases, e. g., sulfonium, or a mixture comprising two or more of these may be employed. Ako it is practical to use a nitrite salt of an amine, the hydrocarbon radicals of which are different, or an amine containing a. plurality of amino groups. A compound employed as an organic base to form a volatile organic nitrite according to the invention may contain an acyclic, alicyclic, or heterocyclic structure or radical. One or more of the hydrogen atoms of the basic nitrogen atom may be substituted with other hydrocarbon radicals which may be heterocyclic, aromatic, acyclic, or alicyclic. The basic nitrogen atom may be part of a heterocyclic ring. The organic substituents on the basic nitrogen atom, may have aliphatic and/or aromatic unsaturations. The organic substituents on the basic nitrogen atom may contain stable polar radicals, e. g. chloro, fluoro, bromo, ether, thioether, alcohol, free amino, ketone, ester, nitrite, cyanate, or nitro groups. In the structures of the above nitrite salt of organic bases, a basic sulfur atom, particularly in the onium form, is suitable as the source of the basicity in the organic structure in place of the nitrogen atom.

Representative classes of organic bases which are suitable for preparing the salts used as vapor phase inhibitors according to the present invention, include: primary amines-secondary amines, tertiary amines, cyclic secondary amines of the type of piperidine, piperazine, oxazines, morpholine, thiazolines, and pyrrolidine; and various nitrogenous bases such as urea, thiourea, hydrazines, hydroxylamines, amidines, and guanidine. In any the above nuclei, alkyl, cycloalkyl, terpinyl, bomyl, aralkyl, benzyl, phenyl, aryl, and various substituent groups or atomic radicals may be present so long as the sum total basicity of the nitrogenous compound is approximately equal to or greater than the acidity of nitrous acid with which it Iorms a salt. Among the substituent groups the alkyl and cycloalkyl groups are preferred.

.The basicity of the various basic constituents of the class of salts described herein is described, for example, in The Organic Chemistry of Nitrogen" by N. V. Sidgwick, 1937 edition and in "Organic Chemistry by Paul Karrer, 1938 edition.

Spec c examples or organic nitrogen bases suitable for preparation of the amine-nitrite salt vapor phase corrosion inhibitors of the present invention include:

Primary 7 amiaa. -Methylamine, isopropyl amine, mambo-butane, tertiary butyl amine, 2-amino-4-lletiiyl-pentane, various amyl, hexyl,

heptyl, oetyl, and higher homologous primaryamines wherein the amino. group is attached to N-methyl N-cycloterpenyl amine,

4 fenchyl amine, cycloterpenyi amincs', pinyl amine, benzylamine, betaphenylethyl amine, alkylated benzylamines, tetrahydro betanaphthylamine, allyl amine, betamethyl allyl amine, beta-chloro allyl amine, and their homologs and analogs.

Secondary amines.Di-methyl, di-ethyl, di-npropyl. di-isopropyl, di-butyl-amines; various secondary amines derived from amyl, hexyl, heptyl, octyl, and higher homologous alkyl groups; methylisobutyl amine, N-methyl, N- tertiary butyl amine, N-alkyl N-cyclohexyl amine, N-alkyl N-bornyl amine, di-bornyl amine, N-isopropyl N-(l) -methyl amine, N-alkyl N-benzyl amines and their homologs and analogs; dicyclopentyl amine, dicyclohexyl amine, alkylated-dicyclohexyl amines; dibenzylamine, di-(beta phenyl ethyl) amine; piperidine, piperazine, allwlated piperidines or piperazines; alkylated and unalkylated oxazines such as morpholine and 2,4,45- tetramethyl tetrahydro-1,3-oxazine; alkylated- 1,3-thiazolines such as 2,4,4,6-tetramethyl tetrahydro-3-thiazolines.

Secondary amine type dzrivatives of alkylene diamines, such as:

wherein R1 and R: may be like or different aliphatic, alicyclic, aralkyl alkarylalkyl, heterocyclic, terpenic radicals, and wherein R: is an alkylene or cycloalkylene radical. These R1 and R radicals for instance may be isopropyl, butyl, cyclohexyl, benzyl, and/or bornyl radicals. The R: radical is preferably an ethylene or propylene radical.

Tertiary amines. -Trimethylamine, triethylamine, tri-n-propylamine, tri-isopropylamine, tributylamine, higher homologous and isomeric trialkylamines, variously N-substituted tertiary amines having different organic radicals on the amino nitrogen atom, e. g. alkyl, alicyclic, bornyl. fenchyl, aralkyl, and like homologs and analogs; and tertiary amine type derivatives of akylene diamines.

Organic nitrogenous bases, particularly guanidine; and also suitable are diazoles, e. g. Z-heptyl- 2-imidazoline, diazines, pyrimidines, and the like are also suitable for forming the nitrite salts.

Quaternary ammonium basea-Tetramethyl and higher tetra alkyl ammonium bases; trimethyl benzyl, trimethyl cyclohexyl, tributyl decyl ammonium bases; various quaternary N- substituted ammonium bases having various oraralkyl group on the quaternary nitrogen atom,

including methyl, butyl, cyclo hexyl, groups and like homologs or analogs.

The invention is preferably practiced by using as the corrosive wear-inhibitor a nitrite salt formed by the addition of nitrous acid to a tri valant basic nitrogen atom of an organic compound. The invention is still more preferably practiced by using as the corrosive wear-inhibitor asecondary amine nitrite which may be aliphatic, cycloaliphatic, and/or heteroalicyclic in character.

The salts of nitrous acid and the organic nitrogcn bases described above, may usually be benzyi prepared by a stoichiometric reaction of an organic nitrogen base with nitrous acid while maintaining the reaction mixture at least slightly alkaline.

any acidity initially present or which may develop in the media, a basic-acting agent may be added. Of the various basic-acting agents which may be employed, organic nitrogenous bases are preferred. More preferably an organic nitrogenous base having a similar or the same molecular structure as that employed to prepare the nitritesalt inhibitor, may be employed. Various specific examples of basic-acting agents suitable for providing a pH of at least 6 are described in the foregoing examples of bases suitable for forming the present nitrite salts. Other basic-acting agents, whether organic or inorganic, and including alkaline soaps, alkaline phenoxides, etc., are also suitable.

As mentioned the invention is applicable to the prevention or marked inhibition of the corrosive wear of moving metal parts which are in contact with other surfaces of corrodible metals. The invention is applicable for instance to prevent corrosive wear in steam turbines, automotive engines, aircraft engines, marine-type engines, gasoline-powered engines of various kinds, and Diesel type engines.

The corrosive wear inhibiting agent may be introduced into the combustion zone of an internal combustion engine in any manner, for example: by introduction together with the air supply, by solution or dispersion in the fuel supplied to the piston, by solution or dispersion in a separate auxiliary liquid, or by separate injection into the piston chamber. 7

The corrosive wear inhibiting agent may be introduced into the internal lubricating flow system of an internal combustion engine, for example, by solution or dispersion in the lubricating fluid, e. g., by incorporating the corrosive wear inhibiting agent in the lubricating oil, or by preparing oil filters which are impregnated with the organic base nitrite and which gradually yield the nitrite to the oil as it circulates through the filter.

Suitable organic lubricating liquids in which the present organic base nitrite anti-wear agents may be incorporated include: petroleum distillates derived from natural sources, synthetic petroleum fractions, and various natural or synthetic organic materials, which may or may not contain other additives, and which have suitable lubricating characteristics such as viscosity. viscosity index, stability, etc. The synthetic petroleum fractions employed in lubricating an internal combustion engine may essentially comprise one or more polymers of propylene, butylene, etc'., preferably fully hydrogenated propylene polymers also a hydrogenated copolymer of propylene and isobutylene. The present anti-wear agents are particularly useful when incorporated in these copolymers. Additionally, waxes or high molecular weight alcohols may be added to a lubricating oil to attain additional anti-wear eil'ects. f the synthetic organic (non-petroleum) lubricants, the rust common are those in which the chain and/or side-chains contain oxygen, sulfur and/or nitrogen atoms. Examples of this class are: oxyhydrocarbons comprising various monoor di-esters, e. g., 2-ethyl hexyl sebacate, dioctyl phthalate, polymers of unsaturated esters such as polyallyl caprylate, esters of the general formula:

coon; R1 coon,

where the R's are organic radicals which may contain hetero atoms and n is 1 or more depending upon the sizes of the R's, polymers of alkylene oxides or alkyleneglycols having the general formula:

polymers of alkylene sulfides or alkylene dithiols having the general formula:

F I X---SR copolymers of alkylene oxides, alkylene glycols, alkylene sulfides, and/or alkylene dithiols having the general formula:

wherein each R is preferably an ethylene or propylene radical though many other organic radicals particularly by hydrocarbon (alkyl or cyclo other organic epioxides are also suitable.

amides such as N,N-diisopropyl lauramide, N,N- diamyl stearamide, N-isopropyl-N-1,3-dimethylbutyl lauramide may in certain cases be used as the lubricating media.

The proportion or amount of the agent which is introduced to suppress the corrosive wear of frictionally contacted metal parts in accordance with the process of the invention, may vary within relatively wide limits. However, it is preferred to add the smallest effective amount. The amount usually employed is between about 0.001 weight percent and about 10 weight percent based on the organic liquid lubricant of the machine, or of the hydrocarbon or other organic fuel. The preferred range is between about 0.1 weight percent and about 2 weight percent. The optimum concentration depends inter alia upon t e degree of corrosive wear-inhibiting activity of the particular organic base nitrite employed, upon the stringency of the conditions under "hich corrosive wear must be prevented, the am unt of moisture and aeration present (particu arly in the lubricating oil, etc.), arid upon the degree of resistance to corrosive wear of the metal rarts themselves (lining the operation of a iven machine.

For purposes of further illustration reference will be made to the following examples, it being understood that there is no intention of being limited to the specific conditions disclosed therein.

' Example I Comparative tests were made in the operation of a Diesel engine under normal conditions and a with morpholine nitrite introduced along with the air supply to the piston and combustion zone of the engine. The vapor of the morpholine nitrite was introduced by placing an excess quantity of crystals of the solid morpholine nitrite in the air cleaner of the engine. At the end of thirteen hours of operation, it was found that the piston ring wear, as determined by the total weight loss of the piston rings, was approximately 17% less when the engine was operated with the vapor of the described morpholine nitrite salt, as compared to the case where no inhibition was introduced into the piston chamber.

Example 1! of a spark ignition internal combustion engine, operated with and without the addition of morpholine nitrite. salt which was dissolved in the gasoline fuel supply introduced to the piston and combustion zone. In these tests, the engine was operated for alternate 20 hour periods first with an untreated gasoline fuel, and then with the same fuel containing 0.1 mg. of morpholine nitrite per 100 ml. of gasoline. It was found that the piston ring wear, as determined by the total weight loss of the piston rings, averaged approximately 20% less during the periods when the engine was operated with, morpholine nitrite salt contained in the gasoline fuel, as compared to the wear produced when no morpholine nitrite was used.

Emmple III Five hundredths of a gram of dicyclohexylammonium nitrite was mixed with 45 ml. of a white highly refined mineral oil in a 4 oz. oil sample bottle. Five ml. of distilled water was added to the oil and a 5 inch length of coldrolled steel rod was cleaned with a grease solvent and acetone, then dried, and placed in the bottle. Another test was prepared in the same manner but without the amine nitrite salt. The bottles were rotated end-over-end at 60 R. P. M. for 24 hours at a temperature of 150 F. The steel rod from the test with dicyclohexylammonium nitrite did not rust, while the control rod in the oil and water alone had numerous rust blisters distributed generally.

The present application is a continuation-inpart of the copending application Serial No. 557,358, filed October 5, 1944, and now abandoned.

We claim as our invention:

1. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine a wear-inhibiting amount of an organic base nitrite having a vapor pressure of at least 0.00002 mm. Hg at 21 C.

2. In the operation of an internal combustion engine, the step of introducing directly into the combustion chamber of said engine during the normal operation thereof a wear-inhibiting amount of an organic nitrogen-base nitrite having a'vapor pressure of at least 0.00002 mm. Hg at 21 C.

3. In the operation of a machine having movable metal parts in moving frictional contact during normal operation thereof, the step of in- I .8 troducing into the proximity of said metal parts an atmosphere containing a wear-inhibiting amount of a nitrite salt of an organic trivalentnitrogen base, said salt having a vapor pressure of at least 0.00002 mm. Hg at 21 C.

4. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine a wear-inhibiting amount of a nitrite salt of a secondary amine, said salt having a vapor pressure of at least 0.00002 mm. Hg at 21 C.

5. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine a wear-inhibiting amount of di-isopropyl amine nitrite.

6. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine a wear-inhibiting amount of di-cyclohexyl amine nitrite.

7. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine a wear-inhibiting amount of morpholine nitrite.

8. In the operation of an internal combustion engine, thestep of introducing into the combustion chamber of said engine during the normal operation thereof a fuel therefor containing a wear-inhibiting amount of an organic nitrogenbase nitrite salt having a vapor pressure of at least 0.00002 mm. H8 at 21 C.

9. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine during the normal operation thereof a fuel containing a wearinhibiting amount of a nitrite salt of an organic trivalent-nitrogen base, said salt having a vapor,

pressure of at least 0.00002 mm. Hg at 21 C.

10. In the operation of an internal combustion engine, the step of introducing into the combustion chamber of said engine during the normal operation thereof a fuel therefor containin a wear-inhibiting amount of di-cyclohexyl amine nitrite.

11. In a process for inhibiting corrosive wear of moving metal parts of an internal combustion engine, the improvement which comprises the use of a fuel containing a wear-inhibiting amount, at least about 0.001% by weight, of dicyclohexyl amine nitrite in the combustion zone of said engine.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,809,833 Davenport June 16, 1931 2,308,282 Howland Jan. 12, 1943 2,321,517 Rosen June 8, 1943 2,333,206 Sloan Nov. 2, 1943 2,385,158 Paulsen Sept. 18, 1945 2,388,132 Fischer Oct. 30, 1945 2,433,243 Smith Dec. 23, 1947 2,433,716 Smith Dec. 30, 1947 

1. IN THE OPERATION OF AN INTERNAL COMBUSTION ENGINE, THE STEP OF INTRODUCING INTO THE COMBUSTION CHAMBER OF SAID ENGINE A WEAR-INHIBITING AMOUNT OF AN ORGANIC BASE NITRITE HAVING A VAPOR PRESSURE OF AT LEAST 0.00002 MM. HG AT 21* C. 